Remedy for Wall Thinning in Pipelines
Intelligent pigs are increasingly used in pipe line integrity management to assess the integrity of pipeline walls. Depending on their type and size and if safety relevant, the pipe wall defects detected in these assessments need to be repaired. Previously, pipeline operation had to be interrupted to carry out these repairs. Depending on the pipe‘s service diameter, repair sometimes involved considerable product losses.
Successful solution: Hot Sleeves
Pipes with defects were generally removed and replaced by a new spool. Alternatively, a split locking ring was welded onto the pipe. This procedure involves considerable efforts, in particular for large diameter pipes, and is not the best method of repair with regard to pipe stress. In contrast, metal loss or laminations can be efficiently repaired with the „Hot Sleeves“ procedure developed by TÜV SÜD using heat-shrink sleeves.
How does the procedure work?
In the Hot Sleeves procedure, two half shells made of the same material and with the same wall thickness as the pipe to be repaired are fitted around the pipe defect and then evenly heated. The defined heat input causes the shells to expand longitudinally and, after welding of the longitudinal seams, to precisely fit the pipe wall to be repaired. Subsequent cooling causes the shells to fit snugly around the pipe. Through appropriate dimensioning of the sleeve, any impermissible elongations and stresses up to the permissible upper yield point of the pipe to be repaired can be absorbed.